Multiple Laser Attenuation Technique for Determination of Monodispersity within Suspended Droplet Clouds

The monodispersity of suspended droplets or particles within aerosols is an important characteristic for certain combustion experiments. In a fundamental study of laminar flame combustion of droplet and vapour mixtures, the droplet clouds or aerosols must be at a condition close to mono-disperse or narrow spatial distribution of size in order to systematically characterize the effect of droplets on combustion. In order to determine the monodispersity of the aerosols, a few measurement techniques such as the Phase Doppler Anemometer and Malvern Particle Sizer can be considered. However, these commercially available measurement systems have several disadvantages besides being very costly. In the present work a technique based on the laser attenuation or light extinction principle is experimented for the determination of monodispersity within aerosols or droplet clouds. The laser attenuation system is supported by a He-Ne laser that is collimated by a set of optical lens. As the laser passes through the droplet clouds, it is partially absorbed by the droplets, resulting in a lower light intensity. The results are presented in terms of light attenuation, which also implies the amount of droplets in the system. With the use of multiple lenses and light power meters that are mounted at various locations, the spatial distribution of light intensities that pass through droplet clouds could be measured. It is shown that this technique has the potential for use in the determination of monodispersity of aerosols with the advantage of low cost and simple setup.